Home > Protocols > Technical tips for 8-OHdG ELISA Rev.080613
Technical tips for New 8-OHdG Check ELISA/oxidative sress markers/oxidative stress test  
New 8-OHdG Check ELISA kit is designed to be used easily. Followings are technical tips to have the best results using this product. Please read the instruction manual enclosed in the product package.

These tips may be useful in using other ELISA products such as 'Highly Sensitive 8-OHdG Check' and 'HEL ELISA kit'. Please confirm that some experimental conditions are different from that of 'New 8-OHdG Check'.
Open package of 'New 8-OHdG Check'
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Bring out the package from refrigerator, and stand for 1 hour at room temperature.
Open the package. Conponents which will not be used in 2 hours should be stored at refrigerator.
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Preparation of 8-OHdG pre-coated micro plate wells
oxidative sress markers/oxidative stress test
oxidative sress markers/oxidative stress test
Remove the desiccant attached at the base of the plate. If you are planning to use some wells on the other day, please remove strip wells from the frame, and store at 4 °C in the bag.
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Pour samples and standards to micro plate wells
8-OHdG ELISA procedure /oxidative sress markers/oxidative stress test
8-OHdG procedure vial /oxidative sress markers/oxidative stress test Prepare primary antibody reagent. Mix one vial of primary antibody solution to primary antibody vial.
Pour 50 micro L of samples and standards to wells accurately. Inaccuracy of the pipette volume may cause errors of 8-OHdG results. In some cases, 'edge effect' can be observed at upper and bottom row.
Please take care that samples and standards must be applied to the well first, and subsequently primary antibody reagent.
8-OHdG ELISA procedure /oxidative sress markers/oxidative stress test
Primary antibody
8-OHdG ELISA procedure pipetting /oxidative sress markers/oxidative stress test
Start antigen-antibody reactions by pouring 50 µL of primary antibody reagent to all well but blank well. Instead of primary antibody reagent, 100 µL of PBS or wash buffer should be poured to blank well.

Inaccuracy of the pipette volume may cause errors of 8-OHdG results. The bottom and side wall (up tp 5mm from the bottom) of the wells, 8-OHdG antigen is precoated. Please take care not to touch or scrape by pipette tips.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure shaking /oxidative sress markers/oxidative stress test
Tap the side of the plate gently for 3 to 5 times, and mix the content of wells.
8-OHdG Assay procedure next step /oxidative sress markers/oxidative stress test
Primary antobody reaction
8-OHdG ELISA procedure temperarure contarol /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure sealing /oxidative sress markers/oxidative stress test
Seal the plate tightly.

Incubate for one hour (50-70 minutes) in the water bath or incubator controled at 37 °C. Please take care to incubate not longer than 70 minutes.

Temperature control is very important for the reproducibility of data. Please take care that the temperature is controlled uniformly. If your results would not be stable, please try water bath.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA anti-mouse IgG HRP conjugated /oxidative sress markers/oxidative stress test
Prepare secondary antibody reagent.
 
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Washing
8-OHdG ELISA procedure plate handling /oxidative sress markers/oxidative stress test
Hold the plate tightly to prevent the splits falling.

About washing machines and aspirators
Use of automatic washing machines or aspirators may result in high background, and not suitable for 8-OHdG ELISA. Please wash the plate manually.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure plate handling2 /oxidative sress markers/oxidative stress test
Put the micro plate upside down, and swing to discard the reagent.

Take care
This process is very important for reproducibility and blank. This product is based on competitive ELISA system, and very sensitive for trace well-to-well cross contamination of primary antibody.

Advice to obtain stable data
1) Please swing vigorously, and discard reagent.
2) Hold the plate contiously upside down, and put on new paper towels to remove water drop.
3) Pat the plate to the paper towel.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure washing the plate /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure cleaning the plate /oxidative sress markers/oxidative stress test
Tap the plate to new paper towels vigorously for 5 times, and remove water drop.

Please take care not to dry up. Don't touch or wipe inside the wells. Replace the paper towel when it becomes wet or polluted.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure pipetting /oxidative sress markers/oxidative stress test
Pour diluted washing reagent 250 µL/well using 8 channel pipette.
Washing reagent should be poured into the well in 3 minutes not to dry the well.

NOTE: Dried wells may cause non-specific increase in absorbance or instability of data.

Take care for the first washing
As mentioned above, this product is based on competitive ELISA system, and very sensitive for trace contamination of primary antibody between wells. Please take care not to touch the pipette tip to the wells, to prevent well to well transfer of primary antibody mediated by pipette tips. Contamination of primary antibody may cause increase in absorbance at blank well.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA shaking the plate /oxidative sress markers/oxidative stress test
Shake the plate slowly.

Perform washing process for 3 times as described above.
Finally, discard washing reagent from wells, and remove water drop from the inside of the well.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Secondary antibody
8-OHdG ELISA procedure secondary antibody /oxidative sress markers/oxidative stress test
Pour secondary antibody reagent 100 µL/well to all well.
Please take care not to dry inside wells.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure washing the plate /oxidative sress markers/oxidative stress test
Tap the side of the plate gently for 3 to 5 times, and mix the content of wells.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Secondary antobody reaction
8-OHdG ELISA procedure incubation /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure seating the wells
Seal the plate tightly.
Incubate for one hour (50-70 minutes) in the water bath or incubator controled at 37 °C. Please take care to incubate not longer than 70 minutes.

Temperature control is very important for the reproducibility of data. Please take care that the temperature is controlled uniformly. If your results would not be stable, please try water bath.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Washing
8-OHdG ELISA procedure holding the plate wells /oxidative sress markers/oxidative stress test
Hold the plate tightly to prevent the splits falling.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure wasing the plate  2nd /oxidative sress markers/oxidative stress test
Put the micro plate upside down, and swing to discard the reagent.
8-OHdG ELISA next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure washing the plate 3rd /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure tapping the plate /oxidative sress markers/oxidative stress test
Tap the plate to new paper towels vigorously for 5 times, and remove water drop.

Please take care not to dry up. Don't touch or wipe inside the wells.

NOTE: Replace the paper towel every time. Residual secondary antibody may cause non-specific increase in absorbance or instability of data.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure TMB substrate /oxidative sress markers/oxidative stress test
Pour diluted washing reagent 250 µL/well using 8 channel pipette.
Washing reagent should be poured into the well in 3 minutes not to dry the well.

NOTE: Dried wells may cause non-specific increase in absorbance or instability of data.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure stop solution /oxidative sress markers/oxidative stress test
Shake the plate slowly.

Perform washing process for 3 times as described above.
Finally, discard washing reagent from wells, and remove water drop from the inside of the well.

NOTE: Please use new paper towels to prevent trace contamination of secondary antibody.

8-OHdG ELISA procedure measurement /oxidative sress markers/oxidative stress test
Prepare substrate solution.
8-OHfdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure calibration /oxidative sress markers/oxidative stress test
Please confirm that water drop is not exist inside the wells.

NOTE: Residual water drop may cause non-specific increase in absorbance.
8-OHdG ELISA procedure results/oxidative sress markers/oxidative stress test
Substrate solution
8-OHdG ELISA procedure pour the substrate /oxidative sress markers/oxidative stress test
Pour substrate solution 100 µL/well to all well.
Please take care not to dry inside wells.
8-OHdG ELISA next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure shaing the plate /oxidative sress markers/oxidative stress test
Tap the side of the plate gently for 3 to 5 times, and mix the content of wells.
8-OHdG ELISA procedure next srep/oxidative sress markers/oxidative stress test
Substrate reaction
8-OHdG ELISA procedure final step /oxidative sress markers/oxidative stress test
Incubate for 15 minutes at dark place. Please take care that not to prolong the reaction time.

NOTE: Substrate solution can react faster depending on the temperature. If the room temperature is high (> 25 °C), please try to shorten the reaction time from 15 minutes to 10-13 minutes.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure stop the reaction /oxidative sress markers/oxidative stress test
Add 100 µL of reaction terminating solutuion to all well.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure micro plate reader /oxidative sress markers/oxidative stress test
Measure aabsorbance at 450nm by micro plate reader.
Draw standard curve, and calculate 8-OHdG concentration in samples.
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Typical standard curve
The absorbance at 0.5 ng/mL of 8-OHdG standard is designed to be between 1.6 and 2.0 at 25 °C. But it may be 1.4 to 2.2 depending on experimental conditions such as room temperature.
8-OHdG ELISA procedure calibration plot /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure get the results /oxidative sress markers/oxidative stress test
8-OHdG ELISA procedure next step /oxidative sress markers/oxidative stress test
Trouble shooting
a) High absorbance, but can draw standard curve: Try to shorten substrate reaction time.
b) Absorbance at blank well is too high: Please check washing process.
c) Please don't mix reagents from different lot.
d) Please confirm that sample pretreatment is done correctly. In some cases insluble materials can be observed when urine sample is thawn. Please remove insoluble materials by centrifugation.
e) To detect 8-OHdG in serum samples, please remove proteins by ultra filtration before assay.
f) To prevent errors in reproducibity, triple assay (N=3) is recommended for at least standards
g) If abnormal results are expected, please try to dilute samples by PBS(pH7.4).
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8-OHdG ELISA procedure explaining /oxidative sress markers/oxidative stress test
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